This application claims priority to German Patent Application DE10160996.5, filed Dec. 12, 2001, the entirety of which is incorporated by reference herein.
This invention relates to a device for air mass flow control.
The provision of air systems, in particular cooling-air systems for gas turbines, is known from the state of the art. These systems, in particular those provided for cooling purposes in the hot section of the engine, are dimensioned or designed such that they give adequate cooling also under the most adverse conditions, for example at maximum power and the associated highest temperature ranges.
Many of these air systems are not designed adaptively, which results in excessive air mass flow and overcooling under part-load operating conditions or operating conditions requiring lesser cooling. As a consequence, a larger air mass than actually required is supplied to the turbine.
Disadvantageously, with an excessive cooling-air mass being taken from the compressor, the efficiency of the gas turbine is compromised. This decreased efficiency leads to an increase of the specific fuel consumption of the gas turbine, with the consequence that costs increase and the aircraft range is reduced.
Designs are known in state of the art in which valve elements, flaps or similar de-vices provided in the respective air ducts can be opened or closed by means of a separately controlled or governed actuator. Reference is here made to the U.S. Pat. Nos. 4,462,204 and 4,807,433, as well as U.S. Pat. No. 6,202,403, for example. These arrangements, however, incur high manufacturing effort and operational complicacy due to the necessity for appropriate governing or controlling means.
In a broad aspect, the present invention provides a device for air mass flow control that, while being simply designed and easily and safely operable, is self-controlling and enables the cooling-air mass flows to be accommodated automatically.
It is a particular object of the present invention to provide means for the solution of the above problem by the present invention featuring the characteristics described herein, with further advantages and aspects of the present invention becoming apparent from the description below.
The present invention accordingly provides a device for air mass flow control with at least one inlet duct which issues into an air duct or the like. The present invention furthermore provides for a counter-pressure duct which is located downstream of the mouth of the inlet duct and branches off from the air duct.
The present invention also covers a double-acting shut-off element that is connected between the counter-pressure duct and the inlet duct and is movable to control the flow in the inlet duct.
The present invention is characterized by a variety of merits.
The adaptive, self-controlling design of the device ensures that it automatically adjusts to the respective operating points or operating conditions of the gas turbine. Thus, the supply of cooling-air is accommodated to the actual demand. Accordingly, removal of an excessive air mass from the compressor is avoided. As a consequence, overall efficiency of the gas turbine increases and fuel consumption de-creases accordingly, for example at cruising speed.
The arrangement according to the present invention, therefore, makes use of the pressure differences which occur in the engine in dependence on the respective operating point to control or govern the shut-off element. The present invention accordingly provides for a very simple, mechanical means of control, fully dispensing with additional electronic monitoring or control/governing devices.
In a particularly advantageous form, the shut-off element includes a double-action piston-cylinder unit. Thus, a pressure-controlled metering valve is provided which can have high simplicity of design and construction and high reliability of operation. Shut-off elements of this type enable the individual components of a gas turbine to be separately supplied with cooling air.
The entire arrangement can be manufactured in a very easy and cost-effective way and requires low maintenance effort.
In a particularly favorable design, the piston itself provides the means for flow control. In such a design, additional shut-off elements or similar means are not required. In a favorable form, the piston itself can be brought into the flow area of the inlet duct, or air duct, as a shut-off element to control its cross-section and, thus, the air mass flow.
In an alternative form or development of the present invention, provision can also be made such that the means for flow control can include additional structure to control or govern several inlet ducts. It may in this case be favorable to provide a slider-type element, an annular element or a similar means to enable control of several cooling-air ducts at the same time.
Since the varying pressure differences encountered are used as input variable, the device according to the present invention provides both for continuous and staged control of the cooling-air mass flow.
The device according to the present invention is, therefore, a self-contained control/governing system which does not require external actuation or similar means.
In accordance with the present invention, the device can be used either locally for the control of the cooling-air mass flow of an individual component or for the control of cooling-air flows of a plurality of components, for example cooling-air flows in annuli or the like.
With regard to the underlying technical principle, the amount of the pressure difference is not crucial for the operation of the device.
Summarizing, then, the reduction of the cooling-air mass flows gives rise to an in-creased efficiency of the gas turbine. This provides for lower fuel costs and enables longer flight missions to be executed.